A colored filter is primarily composed of a substrate, a black matrix, a colored film layer, a protective layer and a conductive layer. Usually, a colored photoresist composition is applied to a substrate to form a photoresist layer, a pre-determined photoresist pattern is formed after exposure of the photoresist layer, and the photoresist pattern is developed and post-baked to obtain the colored film layer.
In a colored filter, there are requirements on the slope angle of the aforesaid film layer. If the slope angle is too large, it is prone to leaking light. The slope angle of a film layer primarily depends on the film forming property of the photoresist composition. The major components of a photoresist composition include an alkaline soluble resin, a photoactive compound, a photoinitiator, a pigment dispersion solution, an organic solvent as well as other additives. After exposure and experiencing a high temperature post-baking, the photoactive compound will form a polymer. Some polymers have high hardness and are not easy to be bent to form a gradient, causing a large slope angle of the film layer. Therefore, gaps may form in the junction between the colored film layer and the black matrix, thereby causing light leakage. Moreover, a large slope angle affects the coating and the rubbing effect of the orientation layer in the liquid crystal glass box in subsequent process, which may also cause light leakage. It may even affect the orientation of liquid crystals, thereby affecting the display quality of the images. It thus becomes a concern to keep the slope angle of the colored film layer within a proper range (23°-60°) in the research and development of a photoresist composition.